The present invention relates generally to chemical mechanical polishing of substrates, and more particularly to a retaining ring for use in chemical mechanical polishing.
Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. After each layer is deposited, the layer is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the outer or uppermost surface of the substrate, i.e., the exposed surface of the substrate, becomes successively less planar. This non-planar outer surface presents a problem for the integrated circuit manufacturer as a non-planar surface can prevent proper focusing of the photolithography apparatus. Therefore, there is a need to periodically planarize the substrate surface to provide a planar surface. Planarization, in effect, polishes away a non-planar, outer surface, whether a conductive, semiconductive, or insulative layer, to form a relatively flat, smooth surface.
Chemical mechanical polishing is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head, with the surface of the substrate to be polished exposed. The substrate is then placed against a rotating polishing pad. The carrier head may also rotate and/or oscillate to provide additional motion between the substrate and polishing surface. Further, a polishing slurry, including an abrasive and at least one chemically reactive agent, may be spread on the polishing pad to provide an abrasive chemical solution at the interface between the pad and substrate. In addition, the polishing pad may be periodically conditioned to maintain a uniform polishing rate.
In one aspect, the invention is directed to a retaining ring for use on a carrier head in a chemical mechanical polishing apparatus. The retaining ring includes an annular ring having a bottom surface, an inner surface and an outer surface, and a plurality of recesses on the bottom surface. Each recess includes an inner trailing surface, a slurry capture area, and a channel connecting the slurry capture area to the inner surface.
Implementations of the invention may include one or more of the following features. The inner trailing surface may incline backward and form an acute angle with respect to the bottom surface or incline forward and form an obtuse angle with respect to the bottom surface. The inner trailing surface may be configured for fastening thereon an insert tool having a contact edge for abrasively contacting a polishing pad on the chemical mechanical polishing apparatus. The annular ring may be constructed from a material selected from a group consisting of polyphenyl sulfide (PPS), polyimide, polybenzimidazole (PBI), polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), polycarbonate, acetal, polyetherimide (PEI), or combinations thereof. At least one of the recesses may have a shape designed for nesting, and may be positioned on the bottom surface nested with at least another recess. The total recessed area covered by the plurality of recesses may constitute between 20% to 80% of the total projected surface area of the bottom surface. The channel may be positioned in a plane that is essentially parallel and at a distance from the bottom surface. Each recess may have a three-dimensional shape designed to maintain the functional performance of the retaining ring as a thickness of the retaining ring shrinks. Each recess may have a slurry feeding area, which can include an opening on the outer surface of the annular ring. A total surface area of all the openings on the outer surface may constitute between 20% to 80% of the total projected surface area of the outer surface. The inner surface may include a cut connecting to the channel. Each recess may include an outer trailing surface. The outer trailing surface may incline backward and form an acute angle with respect to the bottom surface, or incline forward and form an obtuse angle with respect to the bottom surface. An insert tool may be fastened on the inner trailing surface. The insert tool is made from a metal carbide. A surface of the insert tool may be treated to enhance wear resistance. The insert tool may have a contact edge including a single contact point, or multiple contact points. The insert tool may have an end in the form of a scraper blade, or an end in the form of a rounded peak. The insert tool may have a head that includes a rounded surface and a tilted surface. The insert tool may have a shoulder forgetting a height of a contact edge with respect to the bottom surface.
In another aspect, the invention is directed to a retaining ring for use on a carrier head in a chemical mechanical polishing apparatus. The retaining ring has an annular ring having a bottom surface, an inner surface and an outer surface, and a plurality of recesses on the bottom surface. Each recess includes an inner trailing surface configured for fastening thereon an insert tool having a contact edge for contacting abrasively a polishing pad on the chemical mechanical polishing apparatus.
Implementations of the invention may include one or more of the following features. An insert tool may be fastened on the inner trailing surface. The insert tool may be made from metal, and at least a portion of the surface of the insert tool may be coated with diamond. The insert tool may have a sharp edge coated with a diamond layer, or a rounded surface coated with a diamond grit. The insert tool may have a contact edge including a single contact point or multiple contact points. The insert tool may have an end in the form of a scraper blade or in the form of a rounded peak. The insert tool may have a head that includes a rounded surface and a tilted surface. The insert tool may have a shoulder for setting a height of a contact edge with respect to the bottom surface.
In another aspect, the invention is directed to a retaining ring for use on a carrier head in a chemical mechanical polishing apparatus. The retaining ring includes an annular ring having a bottom surface, an inner surface and an outer surface, and a plurality of recesses on the bottom surface. Each recess includes an inner trailing surface, an outer trailing surface, and a slurry capture area between the inner trailing surface and the outer trailing surface. A plurality of openings on the inner surface connect with the slurry capture area.
Implementations of the invention may include one or more of the following features. The inner trailing surface may incline backward and form an acute angle with respect to the bottom surface, or incline forward and form an obtuse angle with respect to the bottom surface. The outer trailing surface may incline backward and form an acute angle with respect to the bottom surface, or incline forward and form an obtuse angle with respect to the bottom surface.
The retaining ring and the slurry capture area may provide one or more of following advantages: (1) improved uniformity of the polishing rate over different areas on the substrate; (2) more efficient use of slurry; (3) the polishing pad can be in situ conditioned; (4) extension of the useful lifetime of the retaining ring; (5) reduced defects on the substrate; and (6) reduced consumption of deionized water for rinsing the substrate.
Additional advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized by means of the instrumentalities and combinations particularly pointed out in the claims.